Presto! Space-Time Blurriness Vanishes
Physicists have been knocking themselves silly devising theories to show how, in the tiny world of electrons, quarks, and gluons, the fabric of space is full of gaps and time appears jittery. Perhaps they can relax now. In February a team of astrophysicists showed that time and space may be smooth after all.
Using the Hubble Space Telescope, Richard Lieu of the University of Alabama at Huntsville and his colleagues snapped images of a galaxy located 4 billion light-years away. It was a perfect test case: The “foamy” texture of space-time was expected to slightly alter the speed of light waves as they traveled across such a vast distance.
Collectively, the effect would be to throw the waves of light from the galaxy out of phase; waves that started out even and lined up would be out of step with one another when they reached Earth. Lieu expected this effect would produce a slight blurry distortion around the galaxy. Instead, he saw a distinctive pattern that can be produced only if all the light reaches the telescope at precisely the same time. No blurriness, no foaminess.
The results, which were reproduced in March by a separate European team, raise serious questions for astronomers as well as physicists. If space-time is smooth, black holes cannot exist, and the Big Bang couldn’t have happened. “Without fuzziness, all of the matter and energy of the universe has to be packed, at the moment of creation, into a volume that is zero, with infinite temperature and infinite density. It is an impossible thing to contemplate, and it cannot be reconciled with the current Big Bang theory,” Lieu says.
The theorists are not worried. “The best models of quantum gravity are not ruled out by these results,” says Lee Smolin of the Perimeter Institute, a nonprofit physics institute in Waterloo, Ontario. Y. Jack Ng, a theoretical physicist at the University of North Carolina at Chapel Hill, regards the findings as fundamentally flawed.
Space-time foaminess will have a random effect on light waves, he says, speeding them up at some times and slowing them down at others. Because of this mixed effect, a wave will fall out of phase with its neighbors much more slowly than Lieu’s team figured. “They overestimated the cumulative blurring effect, by a factor of at least a thousand trillion,” Ng says. “No wonder they didn’t find it.”
We Can See Clearly Now
The Milky Way galaxy is so dusty that most light telescopes can’t get a sharp picture of it. However, the Two Micron All Sky Survey (2MASS), begun five years ago, has been exploiting the ability of longer-wavelength infrared light to slip past the debris and create clearer images.
In March a dramatic composite portrait based on millions of images collected by two 1.3-meter telescopes in Arizona and Chile was released. At the center is the Milky Way galaxy; the rusty blush through the middle is composed of dense dust clouds. More than 1 million galaxies, color coded by distance, also appear.
Those in blue are nearest, the green are at a moderate distance, and the red are farthest away. The portrait shows “the texture of the universe,” says Michael Skrutskie, head of the survey’s science team. “It is a relic of the beginning of the universe, when tiny fluctuations in density grew to become clusters of galaxies, and filaments of clusters, and voids between filaments. By analyzing the distribution of galaxies in the sky, we can tell something about what those original fluctuations were.”
Neptune Rocks Early Solar System
Today our solar system looks calm and orderly, but Rodney Gomes has found evidence of its chaotic beginnings. Gomes, a planetary scientist at the National Observatory in Rio de Janeiro, has been studying the Kuiper belt, a group of asteroids orbiting beyond Pluto. In February he announced that some of these objects originated much closer to the sun but were exiled into darkness by Neptune’s gravity.
Astronomers have recently realized that the Kuiper belt contains two populations. One consists of grayish rocks that circle the sun in the same plane as Earth. The other, a rakishly red group, zings around on trajectories tipped as much as 40 degrees from horizontal. The origin of the off-kilter bodies has been a mystery. To have their orbits so skewed, these asteroids must have encountered something with serious gravitational oomph—a planet, for example. Neptune has the requisite mass, but it seemed too far away to cause trouble.
When Gomes ran computer simulations, he realized Neptune probably was the culprit after all. The second group could have formed near Neptune and then been knocked out to distant, tipped orbits when they inched too close to the planet. Gomes’s model implies that the other Kuiper belt objects might also have formed far closer in than they are now. “This means that the disk from which the planets formed was much more compact than usually supposed, with an outer edge where Neptune is today,” Gomes says. “These findings may have implications for how planetary systems around other stars could form and where and how big the planets would be.”
Neutron Star Fizzles
The fate of most stars in the universe, including our own sun, is to implode, collapsing from a huge mass millions of miles across into a sphere barely 10 miles wide that spins around hundreds of times a second. Most of what astrophysicists know about these curious remnants, called neutron stars, is based on theory and limited observations. So researchers were startled to learn in June that the first good measure of a young neutron star’s magnetic field defied all predictions.
Giovanni Bignami, director of the Centre d’Etude Spatiale des Rayonnements in Toulouse, France, aimed a sensitive camera aboard the XMM-Newton orbiting X-ray observatory at a young neutron star labeled 1E1207.4-5209. After three days of tracking, Bignami and his colleagues had collected a detailed X-ray spectrum and a good look at the star’s magnetic field.
Theory predicts that what neutron stars lack in size, they more than make up for in strong magnetic fields, which result from charged particles crackling through the iron crust surrounding the hideously dense ball of uncharged neutrons within the star. Although a typical star has a magnetic field of about 100 gauss, neutron stars are thought to have magnetic fields of up to 1 trillion gauss. But Bignami’s team calculated that the magnetic field of 1E1207.4-5209 is one-thirtieth as strong as it should be. “Either it means that the theory is wrong,” says Bignami, or the star “might have a debris disk around it, like a protoplanetary disk or an overgrown system of Saturnian rings, which could create the same effect.”
Plasma Devils Brighten the Sun
In June a team of astronomers announced that new images of the sun’s surface could explain why our star brightens and dims over the course of an 11-year cycle. Using a Swedish telescope built to study the sun exclusively, the researchers recorded enormous walls of plasma, or roiling superheated gases. They extend 200 miles high and up to 1,000 miles wide, covering the sun’s surface like a sheet of bubble wrap.
The team, led by Bruce Lites of the National Center for Atmospheric Research in Boulder, Colorado, and Tom Berger of Lockheed Martin Solar and Astrophysics Laboratory in Palo Alto, California, reported that the sides of the plasma walls were much brighter than their tops. When more of the walls form during the peak of the solar cycle, more of these bright sides can be seen along the rim of the sun. As a result, more of the sun’s radiation heads toward Earth.
“We need to understand exactly what the magnitude of this [radiation] is and whether it is having any effect on our climate,” Berger says.